Ford rear brakes

[wayne petty]

the backing plates are different for the different shoe widths..  

or the wheel cylinders won't line up well..

station wagons use wider rear shoes.. as do some higher horsepower engine versions..
the stock mustang II rear wheel cylinder bore is 7/8..

try a 15/16   RAYBESTOS WC37016      that might be a bolt on increase in rear bore to increase the rear brake bias  application rear AMERICAN MOTORS   CONCORD   1978-1983  

the sedan versions have straight out tube connections like the MII versions. the wagons come out at angles.

https://www.rockauto.com/en/catalog/american+motors,1980,concord,4.2l+258cid+l6,1002935,brake+&+wheel+hub,wheel+cylinder,1952

will these fit .. perhaps.  that is a 1/16" increase in bore size..

i only see one larger than that and if fits toyota tundra rear brakes.  its 1" but it uses metric fasteners and tube fittings.  and might have different piston ends.

these are just thoughts.